7
$\begingroup$

There have been a number of proposed theories about the fate of the universe. And while the heat death theory is now favored, isn't it simply inevitable? Here's what I mean.

Let's assume a big crunch happens. Don't we now have an ultra-massive black hole containing the observable universe? It's going to evaporate due to Hawking radiation. Yes this will take a really long time, but the ultimate fate of the universe is again heat death.

Let's assume the big rip is correct. Again, this is heat death is it not? Everything has expanded out, ripped apart, and only particles remain. Isolated forever and they radiate away any energy they have.

Let's assume no big crunch but no big rip either. Stuff just dies. As things cool over eons, heat radiates away. Either protons decay, or black dwarfs turn into black holes and evaporate over an extreme amount of time, or perhaps we get the supernova at the end of the universe. But since entropy always increases, we'd still eventually get a heat death wouldn't we?

Improve this question
$\endgroup$
1

3 Answers 3

Reset to default
18
$\begingroup$

In the case of a closed universe, ie "big crunch", you don't end up with "a black hole containing the universe" instead the spacetime of the universe curves together, and the universe is finite in time. Just as the big bang wasn't an "explosion in space", but it is the expansion of space and time, and it makes no sense to talk about what happened "before the big bang", so the big crunch isn't the collapse of matter in space to a black hole, but the collapse of all of space time, and it makes no sense to talk about events "after" the big crunch. So no heat death in that scenario

In open universes, and skipping lightly over "Boltzmann brains" and other such imponderables, then heat death is inevitable: the universe must evolve towards a state of maximum entropy

Improve this answer
$\endgroup$
1
  • 1
    $\begingroup$ skipping lightly over "Boltzmann brains" and other such imponderables also seems to skip lightly over the possibility that the universe might eventually (e.g. in 10^10^56 years) recur or spontaneously disprove its own "end". $\endgroup$ Commented yesterday
7
$\begingroup$

Conformal cyclic cosmology is an example of model of a non-heat-death universe that is unbounded in time.

Basically at the point of "heat death", there universe no longer has particles that interact, just photons. Things that describe a scale - time, distance - are lost anywhere near "current scales".

If you "zoom out" on this insanely cold and empty universe to an insane degree in both time and space, the photons are no longer stretched and alone; instead, the universe is insanely hot and dense and active. Each picosecond at this scale might take a googleplex seconds at the "zoomed in" scale.

At these insane scales, the universe is energy-dominated, and looks a lot like our big bang. Probably all but one of the fundamental forces are irrelevant; but that force could exhibit spontaneous symmetry breaking.

We basically get a "hyperscale" new universe "attached" to the cold heat death of a previous universe. The scale of the previous universe is unreachably small in this new physics beyond the "hyperscale big bang" moment.

It then evolves and eventually enters its own cold phase. We can then make another hyper-hyper scale physics and have it describe another aeon attached to the previous universe.

The entropy argument is that entropy always increases, but so long as there is a lower entropy state to reach this doesn't mean everything heat dies. By doing the hyperscale physics transformation of the math we "unlock" an infinite series of lower entropy states for the universe to fall into.

This requires things that aren't known about the universe to be true, such as electron decay to occur.

I'd think that the black hole information bound on a volume of space, together with reversible physics, makes physics matter with infinite computational future history impossible (ie, avoiding a finite future before a freeze)? Which leaves something like CCC? But I'm no expert.

Improve this answer
$\endgroup$
2
  • $\begingroup$ The "zoomed out" universe though has the problem that speed of light is extremely "slow", doesn't it? Isn't any observable universe in the hyperscale universe extremely small?? $\endgroup$ Commented yesterday
  • $\begingroup$ @kutschkem Time is reduced by a similar factor to space; if you redefine the meter at 10^10^100 meters and then define one new second in terms of the new meter... $\endgroup$ Commented yesterday
0
$\begingroup$

I highly recommend reading "Time without end: Physics and biology in an open Universe" by Freeman Dyson, Reviews of Modern Physics, Vol. 51, No. 3, July 1979, its digital object identifier is 10.1103/RevModPhys.51.447. According to my reading of Dyson the answer is negative. My, probably vague, understanding is that this is a very specific kind of big-rip-scenario. And as with the universe's size, in a certain sense, the number of its possible configurations is increasing as well, there is no maximum entropy and the universe could for eternity remain in states distinguishable from heat death.

Improve this answer
New contributor
TLo is a new contributor to this site. Take care in asking for clarification, commenting, and answering. Check out our Code of Conduct.
$\endgroup$

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.